1. Field of the Invention
The invention relates to a magnet assembly for a magnet valve.
2. Description of the Prior Art
A magnet valve is used for instance for controlling the opening and closing motion of an injection valve member of a fuel injector. The magnet valve includes a magnet assembly, which includes an inner pole, an outer pole, and a coil located between them In magnet assemblies of the kind produced in the prior art, the coil is wound onto an electrically insulating coil holder. The coil, together with the coil holder, is inserted into an annular groove in a magnet core. The wall of the groove, which points toward the axis of the magnet core, forms the inner pole, and the opposite wall forms the outer pole. The width of the groove should be selected such that with an internally located coil holder, a gap is embodied between the individual windings of the coil and the outer pole. A disadvantage of the magnet assembly of the kind known from the prior art, particularly for use in fuel injectors, is that it requires a large amount of installation space. The magnet assembly determines the diameter of the magnet valve. Moreover, because of the coil holder made from insulating material, there is only limited thermal conductivity. Particularly in fast-switching magnet valves, this can lead to overheating of the coil. Moreover, because of the need for compactness and because of the dimensions of the coil holder, only a small number of windings is possible. Increasing the number of windings would necessitate a large coil diameter and thus lead to a larger magnet assembly.